Within a turbo fan engine that utilizes a cascade type thrust reverser, there are typically a plurality of blocker doors that deploy inside of a bypass air duct aft of a fan in order to redirect fan bypass air thru a set of cascades that turn the airflow out and forward in order to reverse the thrust direction. Reversing thrust may be done to slow an aircraft after landing.
Referring to FIGS. 1A-1B, a typical cascade type thrust reverser system 100 is shown. The system 100 includes a sleeve 102 that is translated or moved in, e.g., an aft direction in order to expose cascades 104 as part of the deployment of the thrust reverser (FIG. 1B). Similarly, in order to place the thrust reverser in a stowed state (e.g., during flight) the sleeve 102 is translated or moved in, e.g., a forward (FWD) direction, such that the sleeve 102 may close the passage of air through the cascades 104 (FIG. 1A). The length of the sleeve 102 stroke between the stowed and deployed positions is denoted as reference character 102a in FIG. 1B.
A blocker door 108 is typically pivotally attached to the sleeve 102 within the thrust reverser. For example, FIG. 1B illustrates the blocker door 108 of the system 100 hinged to the sleeve 102 near a point 110. Additionally, the door 108 is attached to the inner fixed structure (IFS) 114 of the thrust reverser via a drag link 112 and associated drag link fitting 116. During flight, the door 108 forms, in part, the outer surface of the bypass air duct 124. The drag link 112 crosses this bypass duct 124 in attaching to the WS 114 at the fitting 116. The positions of the blocker door 108 and the drag link 112 in FIG. 1B may be contrasted with their respective positions when the thrust reverser is stowed; the stowed positions are shown in FIG. 1B via reference characters/dashed lines 108′ and 112′, respectively. For purposes of further environmental context, in FIGS. 1A and 1B the IFS 114 is shown in relation to an engine exhaust nozzle 134 and a centerbody 142.
The drag link 112 lies within the airflow and generates drag losses on the engine, resulting in degraded efficiencies. Additionally, any steps and gaps around the blocker door 108 generate aerodynamic disturbances that reduce overall efficiency.